Corrosion resistance of molybdenum-modified Ni-50 laser-clad coatings on 45# steel in concentrated brine

This study aims to enhance the corrosion resistance of Ni50 laser-clad coatings in high-concentration brine. The effects of molybdenum (Mo) addition at varying concentrations (2 wt%, 4 wt%, 6 wt%) on the microstructure, phase composition, and electrochemical corrosion behavior were systematically investigated. Results indicate that the phase composition primarily consists of γ-Ni solid solution with dispersed carbides and borides. Increasing Mo content enhances solid solution strengthening and friction coefficient. At 4 wt% Mo, the coating achieves peak hardness and optimal wear resistance. Crucially, elevated Mo content significantly improves corrosion resistance, with 6 wt% Mo exhibiting the optimal performance. XPS analysis confirms that Mo incorporation facilitates the formation of multivalent molybdenum oxides (MoO₂/MoO₃), reduces passive film defect density, and enhances its physical barrier properties and stability. This mechanism substantially improves the corrosion resistance of the coating in high-concentration brine. • A Ni50+Mo coating was fabricated on 40Cr using laser cladding. • In this paper, the effects of different Mo addition amounts on the corrosion resistance of Ni50 laser cladding were studied, and the corrosion resistance was optimal at 6% addition amount. • The incorporation of molybdenum facilitates the formation of multivalent molybdenum oxides, reduces the defect density of the passive film, and enhances corrosion resistance.